ITMI981997A1 - PROCESS FOR THE PRODUCTION OF THYROID HORMONES - Google Patents

Description

Description of the industrial invention entitled: "PROCESS FOR THE PRODUCTION OF THYROID HORMONES"

The present invention relates to a process for the production of thyroid hormones and / or their derivatives.

The sodium salt of the levo isomer of thyroxine, as well as the triiodothyronine levo, are used in the treatment of alterations due to hypothyroidism such as goiter, thyroid hypofunction, inflammation of the thyroid and prophylaxis of relapses after surgery. While for attack therapies it is useful to resort to triiodothyronine, for maintenance therapies it is preferable to resort to thyroxine whose action, slower and longer, allows greater manageability of the drug.

The levo form of thyroxine is twice as active as the racemic form, while the right form has only a small physiological activity; therefore the levo forms of triiodothyronine and thyroxine are used as thyroid hormones while the right form of thyroxine is advantageously used in the production of antihyperlipoprotein agents.

In the past, the sodium salt of the amino acid L-thyroxine was mainly obtained from thyroid extracts from domestic animals.

Shiba et al. (Arch. Biochem. Biophys., 140, 90 (1970)) proposed a model of non-enzymatic biosynthesis of thyroxine starting from 3,5-diiodo-L-tyrosine in which the product was isolated with an overall yield of 8% .

The article by Chalmers et al., J. Chem. Soc. 1949, 3424 reports the first systematic synthesis in which levo-thyroxine and its sodium salt are obtained with a total yield of 26% starting from L-tyrosine.

This process, summarized in the following Scheme 1,

includes the following stages:

a) nitration with HNO3 of L-tyrosine (compound 1) suspended in H2SO4; b) protection by acetylation with acetic anhydride of the amino group of L-tyrosine;

c) esterification with ethanol, in the presence of p-toluenesulfonic acid, of compound (III);

d) preparation of the diphenylether (compound V) by reaction of the ester of formula (IV) with p-toluenesulfonyl chloride in pyridine and reaction of the adduct obtained with p-methoxyphenol;

e) catalytic reduction of the dinitro diphenylether of formula (V) and subsequent conversion of the obtained diamine (compound VI) into the corresponding 3,5-diiodo-L-thyronine (compound VII) by Sandmeyer reaction and subsequent removal of the amino acid protecting groups by treating compound VII with a mixture of hydrogen iodide and acetic acid;

f) iodination of compound VIII with KI3 in ethylamine solution and precipitation of L-thyroxine (compound IX) with HCl at pH 4-5; g) solution of L-thyroxine in ethyl alcohol and 2N NaOH, acidification with HC1 at pH 4-5 of the solution heated to reflux, filtration of L-thyroxine obtained by cooling, addition of the crystalline solid to a boiling sodium carbonate solution, cooling and crystallization of the monosodium salt of L-thyroxine.

This synthesis has undoubtedly constituted a significant advance over the extraction from natural products. However, it involves long and laborious purification steps of the intermediates and implies the use of reagents and / or solvents and reaction conditions that are not compatible with the current regulations relating to the protection of health and the environment and are no longer suitable for a industrial type application.

Improvements to this preparation are reported in US 2,889,363 and US 2,889,364, in which a biomimetic synthesis of L-thyroxine is described, comprising aerobic incubation of N-acyl-3,5-diiode-L-tyrosine and subsequent acid hydrolysis of the N-acyl-thyroxine obtained (yield of the incubation reaction 20-40%). However, the overall yield of the reaction is not mentioned.

WO 96/11904 describes a further improvement to the process indicated above which provides for the preparation of the biphenyl ether of thyroxine by means of oxidative coupling catalyzed by manganese salts of the suitably protected diiode-L-tyrosine. In this process, L-thyroxine is isolated and purified as a solid crystalline hydrochloride which is subsequently transformed into the corresponding sodium salt.

The object of the present invention is a process for the production of thyroid hormones which allows, among others, to obtain L-thyroxine of a considerable degree of purity and with global industrial yields of the order of 35-40%.

Compared to the preparation described by Chalmers et al., J. Chem. Soc. 1949, and briefly reported, the process of the invention allows a significant improvement of the reaction conditions from the point of view of safety and environmental protection, a significant reduction in processing times and costs and the isolation of L-Thyroxine particularly pure with an overall increase in process yield of at least 10-15%. In particular, for example, the process of the present invention generally allows to isolate the products of the subsequent stages of the process by direct crystallization of the same from the reaction mixtures. In this way, the purification of the raw materials is avoided by solubilization in generally organochlorine solvents, washing with acidic and basic aqueous mixtures of the organic phases and any further purification of the residues on the column. In fact, these operations, in addition to considerably prolonging the processing times, lead to the formation of secondary products that are difficult to eliminate.

In the process of the present invention, thyroxine as well as triiodothyronine and / or their derivatives can be conveniently prepared starting from the natural amino acid L-tyrosine with a process that involves the nitration of the amino acid, the isolation of the nitration product as a sodium salt and the appropriate protection of its carboxyl and amino functions by, for example, esterification and acetylation, respectively, of the same. Said esterification can be advantageously carried out using an alcohol and SOC2 and the ester thus obtained is isolated by direct crystallization from the reaction mixture, favored by a simple dilution of the same with water and subsequent cooling. Particularly preferred is the process in which the alcohol used is ethanol and the esterification reaction is carried out using diethylsulfite previously prepared starting from ethanol and thionyl chloride.

In the process of the invention, the amino acid thus protected is reacted with p-toluenesulfonylcoride and p-methoxyphenol, in pyridine, obtaining the corresponding biphenyl ether. According to the literature, after the removal of the pyridine, the raw material was taken up with methylene chloride and the solution obtained was subjected to continuous washing with hydrochloric acid first and then diluted soda. In the process of the invention, however, after removing the pyridine, the residue is taken up with a suitable alcohol and diluted with water and from the hydroalcoholic mixture obtained, buffered with a suitable base, the product crystallizes by simple cooling of the mixture itself. By suitable alcohol we mean a C1-C3 alcohol and said alcohol constitutes from 50 to 90% of said hydroalcoholic mixture. By suitable base is meant, for example, sodium carbonate or bicarbonate or aqueous soda. In the preferred process the alcohol used is ethanol and the mixture is buffered with NaHCX3. Particularly preferred is the process in which ethanol represents 75% of the hydroalcoholic mixture.

In the process of the invention the dinitro diphenylether (compound V) thus obtained is dissolved and hydrogenated in a hydroalcoholic mixture from which the obtained diamine crystallizes directly by cooling. By hydroalcoholic mixture we mean a mixture of water and a lower alcohol C1-C3 in which water can constitute between 0 and 50% of the total. Particularly preferred is the process in which the alcohol used is ethanol and water constitutes 20-30% of said mixture.

The patent GB 671070 reports that the diairanin diazotation reaction obtained is advantageously carried out by adding a solution of said amine in H2SO4 / CH3COOH to a solution of the nitrite in H2SO4 carefully diluted, cold, with CH3COOH. In this patent it is argued that the reaction must be carried out in the absolute absence of water.

We have instead surprisingly found that the diazotation reaction of the previously prepared diamine can be carried out, with excellent results, by direct casting of an aqueous solution of the appropriate nitrite into the solution of the diamine in CH3COOH / H2SO4, and subsequent addition of an aqueous solution. of urea. The aforementioned patent furthermore reports that the decomposition of the diazotation product is advantageously carried out in the presence of an organic solvent immiscible with water in which the diiododiphenyl ether obtained is instead soluble. Also in this case the washing steps of the organic phase and the subsequent purification of the raw material obtained by evaporation of the same and crystallization from ethanol are therefore provided.

In the process of the invention, on the other hand, the diazonium salt thus prepared is poured directly into a solution of ioduring agent dissolved in a suitable solvent and cooled to a temperature between 10 and 25 ° C. By suitable solvent we mean simple deionized water or a mixture of water and a second solvent which favors the precipitation of the iodination product by simple dilution with water and cooling of the reaction mixture itself. The use of said solvent, which allows both a considerable reduction in processing times and a simultaneous increase in yield, characterizes the process of the invention. The solvent to be used in mixture with water is preferably selected from acetic acid and a C3-C6 ketone. Particularly preferred are: acetone and methyl isobutyl ketone. The diiododerivato thus obtained is saponified with a mixture HI / CH3COOH, in the presence of HC1, and the 3,5-diiodothyronine obtained crystallizes by simple dilution of the reaction mixture with water. Said compound is further iodinated with KI3, in the presence, of ethylamine. By acidification of the reaction mixture previously decoloured with sodium bisulfite to pH 5-6, the raw hormone precipitates. In the process of the invention said compound is dissolved in ethanol and soda at a temperature between 40 and 70 and preferably between 50 and 60 ° C. By acidification of this solution with acetic acid it is possible to isolate thyroxine as well as possibly triiodothyronine as free bases.

Most of the secondary products that can be formed during the preparation of L-thyroxine have their own biological activity so it is important that this product is free of it as much as possible. It has been surprisingly verified that if the disodium salt of L-thyroxine is used as a starting product for the preparation of the corresponding monosodium salt, a product of higher purity is obtained, which cannot be obtained starting from L-thyroxine as a free base.

In the process of the invention, therefore, the solution of thyroxine in ethanol and soda is cooled to a temperature between 40 and 5 ° C and preferably between 35 and 15 ° C and the disodium salt of the hormone is isolated as a crystalline solid and filtered. . Said salt is then dissolved in water and the solution obtained is acidified and heated. By adding Na2CO3 and subsequent cooling of said solution to a temperature between 50 and 0 ° C and preferably between 40 and 15 ° C, crystallization of the corresponding salt is obtained. monosodium. A further aspect of the present invention is therefore constituted by the isolation of the sodium salt of L-thyroxine starting from the crystalline solid disodium salt rather than from the corresponding free base. The disodium salt of L-thyroxine, in its crystalline solid form, constitutes a useful intermediate in the process of the present invention. Furthermore, it is new and constitutes a further aspect of the present invention. Said invention furthermore includes the use of the disodium salt of L-thyroxine in crystalline solid form in a process for the production of L-thyroxine both as a sodium salt and as a free base as well as of the disodium salt of L-3,5 , 3'-triodothyronine in crystalline solid form in a process for the production of L-3,5,3 '-triiodothyronine both as a free base and as a monosodium salt. And again, similarly, the use of the corresponding disodium salt of D-thyroxine in crystalline solid form in the preparation of D-thyroxine both as a sodium salt and as a free base. The object of the present invention is, therefore, a process for the preparation of thyroid hormones and / or their salts with alkali metals as well as their derivatives which comprises the following stages:; 1) nitration of L-tyrosine and isolation of the dinitro-derivative ( compound II) as the sodium salt; 2) protection of the amino group of dinitro-L-tyrosine with a suitable protective seal; 3) protection with a suitable protective binding of the carboxylic function of the compound (III) obtained in stage 2; 4) condensation of the product of step 3 (compound IV) with methoxyphenol; 5) reduction, with a suitable reducing agent, of the condensation product, compound V, to the corresponding diamino derivative (compound VI); 6) diazotization with H2SO4 and an aqueous solution of a suitable nitrite of the diamine dissolved in a suitable acid or mixture of acids; 7) iodination of the diazonium salt with a solution of an iodizing agent in a suitable solvent and / or mixture of solvents which favor the precipitation of the derived diiode obtained (compound VII); 8) saponification of the protective groups of compound VII with a suitable acid or mixture of acids; 9) iodination of the saponification product, precipitation of the obtained crude hormone and subsequent purification of the same by crystallization of the corresponding disodium salt; 10) isolation of the sodium salt of said hormone or of the same as a free base starting from the corresponding disodium salt. A further object of the present invention is a process for the production of L-thyroxine which includes the following stages:; 1) nitration with HNO3 at a temperature between 10 and 30 ° C of the L-tyrosine dissolved in H2SO4, solution of 3, 5-dinitro-L-tyrosine obtained in water, neutralization of the solution with a suitable base and isolation of the product as sodium salt; 2) N-acetylation of 3,5-dinitro-L-tyrosine with acetic anhydride and a suitable base followed by acidification of the solution to pH between 1.5 and 2 and isolation of the crystalline product obtained (compound III); 3) esterification of compound (III) with diethylsulfite previously prepared starting from ethanol and SOC12; ; 4) condensation of the compound (IV) obtained in the previous stage first with the adduct formed by p-toluenesulfonyl chloride and pyridine and then with p-methoxyphenol in pyridine, evaporation of the latter at a vacuum of 10-20 mm Hg and an increasing temperature, between 65 and 95 * C, solution of the evaporation residue in a suitable quantity of alcohol, dilution of the alcoholic solution obtained with a suitable quantity of water, plugging of the solution with a suitable base and isolation of the diphenyl ether obtained V) by crystallization of the same from the reaction mixture;

5) catalytic hydrogenation with, for example, palladium carbon, of the compound V dissolved in a suitable water / alcohol mixture heated to a temperature between 55 and 65 ° C and crystallization of the corresponding dianimino derivative (compound VI) by cooling the mixture;

6) diazotization of the previously obtained diamine dissolved in CH3COOH with H2SO4 and with an aqueous solution of suitable metal nitrite, in the presence of urea, and iodination of the diazotation product by casting said mixture in a solution of iodizing agent in water or in a mixture aqueous solution of a suitable solvent which favors the precipitation of the diiododerivato (compound VII) by further dilution of the reaction mixture with water;

7) saponification of the protective groups of compound (VII) with a suitable acid or mixture of acids comprising, for example, the mixture HI / CH3COOH, and HC1, dilution with water of the reaction mixture and crystallization of the product (VIII);

8) Iodination with a suitable ioduring agent, and in the presence of ethylamine, of the diiodothyronine obtained, decolorization of the solution with sodium bisulfite, precipitation with a suitable acid of the crude L-thyroxine and purification of the same by isolation, from a solution of absolute ethanol and NaOH, of the corresponding disodium salt (compound XIII);

9) formation of the monosodium salt of L-thyroxine by adding Na2CO3 to the aqueous solution from the disodium salt XIII, acidified to a pH between 2 and 5 and heated to a temperature between 70 and 100 "C.

10) isolation of L-thyroxine as a pure free base (pure compound IX) by acidification of the solution from the disodium salt XIII with a suitable acid with a pH between 5 and 5.5.

The process object of the present invention can be advantageously used both in the production of L-Thyroxine and / or the corresponding monosodium salt, and in the preparation of triiodothyronine levo, equally isolable both as a neutral compound and as a sodium salt, as well as the corresponding D enantiomers of said compounds and / or derivatives thereof. If this process is used for the preparation of D-thyroxine it is necessary to start from D-tyrosine or to reverse its derivative levo-dinitro to the corresponding right enantiomer. This inversion can be carried out as briefly indicated in scheme 1.

The preferred process of the invention, as well as all the possible applications thereof in the preparation of levo thyroxine and / or its salts or derivatives, of levo triiodothyronine and / or its salts or derivatives or the corresponding D enantiomers thereof, is summarized in the following Scheme 2.

The following examples, which are not intended to be imitative of the applicative potential of the invention, have the purpose of illustrating in more detail some of the best reaction conditions identified by the inventors.

Example 1

Preparation of the sodium salt of 3,5-dinitro-L - tyrosine

210 Kg of concentrated sulfuric acid are loaded into a reactor and, slowly, without exceeding the temperature of 50 ° C, 30 Kg of 1: 1 sulfuric acid are added. It is cooled to 15 ° C and 30 Kg (165.6 moles) of L-tyrosine are added in small portions. 38 Kg of 67% nitric acid are then poured into the mixture obtained in about 4 hours, maintaining the temperature between 15 and 22 ° C. At the end of the casting, the reaction mixture is kept for one hour at said temperature and is then poured, without exceeding 30 ° C, into a second reactor into which 1250 Kg of water had been loaded. Once the casting has been completed, the reaction mixture is neutralized to pH 6.4-6.6 using sodium hydrate 30% (630 Kg). During the casting of the first 500 kg of sodium hydrate, the reaction mixture must be cooled so as not to exceed 30 ° C, while the last kg are added without cooling to allow the temperature of the mixture to reach 40 ° C. Said mixture is then kept stirred for one hour at the pH and temperature indicated by correcting any changes in pH with 30% sodium hydrate or 1: 1 sulfuric acid. The crystalline product is then filtered, washed with water, obtaining 65 kg of wet product (corresponding to 45 kg of dry product) which is used as such in the subsequent preparation of 3,5-dinitro-N-acetyl-L-Trosin. (yield 78%).

HPLC titer: 95.9% (in area%)

[a] <D> 20 = 1.1

TLC: Backing: Merck 0.25mm 60F 254 Silica Gel Plate Eluent: Butyl Acetate: Acetic Acetate .water - 40: 15: 5 Detector: Exposing the plate to ammonia vapor for 10 minutes

Rf = 0.24

Elementary analysis

C H Na N

% calc .: 36.87 2.75 7.84 14.33

% found: 36.80 2.74 7.9 14.30

Example 2

Preparation of 3,5-dinitro-N-acetyl-L-Trosin ethyl ester

4.6 Kg (38.7 moles) of thionyl chloride stirred in a perfectly dry reactor are diluted with 4Kg of absolute ethanol which is charged in about an hour during which the temperature of the solution rises spontaneously to 30-35 "C. At the end of the ethanol casting the solution is slowly heated up to 80 ° C, kept at this temperature for one hour to eliminate all the hydrochloric acid formed from the mass and then it is cooled to room temperature. diethylsulfite thus obtained is poured in 30 - 40 minutes in a solution of 3,5-dinitro-N-acetyl-L-Tyrosine (10 Kg, 32 moles), in ethanol (8 Kg), refluxed where said 3.5 -dinitro-N-acetyl-L-Tyrosine is prepared as described in the literature (J. Chem. Soc. 1949, 3424) starting from the product obtained in Example 1. At the end of the casting the reflux is maintained for further 2 hours, then the mixture is allowed to cool slowly until the first crises are formed stalls of the ethyl ester and then further up to 18-20 ° C. After 2 hours the product is filtered and washed with absolute ethanol and dried obtaining the product in question (Kg 10; 29.3 moles) with a yield of 91.6%

m.p. : 128-129 ° C

[a] <D> 20 = -23.6

TLC: Backing: Merck 0.25mm GF 254 silica gel plate Eluent: Butyl Acetate: Acetic Acetate .water - 40: 15: 5 Detector: Exposing the plate to ammonia vapor for 10 minutes

Rf = 0.76

Elementary analysis

C H N

% calc .: 45.76 4.43 12.31

% found: 45.80 4.42 12.29

Example 3

3,5-dinitro-4-p-methoxyphenoxy-H-acatyl-L-phenylalanine ethyl ester

56 Kg (164 moles) of 3,5-dinitro-N-acetyl-L-Tyrosine and 280 Kg of pyridine are loaded into a first reactor and the solution is heated at 40 ° C until complete solution.

In a second reactor, 30 Kg (242 moles) of hydroquinone monomethylether and 40 Kg of pyridine are charged. The solution is stirred until complete solution.

In a third reactor 33 Kg (178 moles) of p.toluenesulfonyl chloride are charged in 62 Kg of pyridine and the solution is heated to 40 ° C and stirred until solution. The 3,5-dinitro-N-acetyl-L-Tyrosine solution is then quickly poured into the solution contained in the third reactor, allowing the temperature of the mixture obtained to rise up to 60-65 "C. The solution contained in the second is then rapidly added. reactor and the temperature of the mixture is brought to 115-120 ° C. The mixture is kept at this temperature for 140-160 minutes and is then cooled to 55-60 ° C. The pyridine is then removed under vacuum (15 mmHg) and the evaporation residue is taken up with absolute ethanol (170 kg), heated to 60 ° C and diluted with 80 kg of water. The solution is then cooled to 50 ° C and buffered to pH 7-7.2 with 40 kg of bicarbonate of sodium in 80 kg of water. The solution is then cooled to 30 ° C and germinated with the desired product. The temperature is then gradually brought to about -5 ° C. After 4 hours the product is filtered, washed first with water mixture : ethanol 50: 50 then with water only and dried obtaining the p desired product (63 kg, yield 86%).

m.p. : 109.5 - 110.1

[a] <D> 20 = - 26.8

TLC: Support: Merck 0.25mm GF 254 silica gel plate Eluent: hexane: butyl acetate .methanol - 3: 5: 2 Detector: U.V. short wavelength for 30 minutes

Rf = 0.76

Elementary analysis

C H N

% calc .: 53.69 4.73 9.39

% found: 53.72 4.71 9.37

Example 4

3,5-diamino-4-p-! Eethoxyenoxy-N-acetyl-L-phenylalanine ethyl ester

30 liters of absolute ethanol, 7.5 liters of water and 6 kg (134 moles) of 3,5-dinitro-4-p-methoxyphenoxy-N-acetyl-L-phenylalanine ethyl ester are charged into a reactor. After 10 minutes of stirring, the mixture is heated to 60 ° C and transferred, under nitrogen pressure, to a second reactor where a suspension consisting of 400 grams of 5% palladium carbon, 50% % water, in 400 grams of water. The reactor is washed with nitrogen and subsequently with hydrogen, the scrubbing gases are discharged from the reactor vent and then hydrogenation is carried out maintaining the temperature between 60 and 65 ° C. At the end of the hydrogenation the reactor is washed with nitrogen, the solution is filtered through an Osla filter at a temperature between 60 and 65 "C and concentrated under vacuum at a temperature between 30 and 35 'C until a residue with a water content between 50 and 55% which is cooled to 18-20 ° C. The product is filtered, washed with absolute ethanol and dried to obtain 4.7 kg of diamine (yield 90%).

m.p. : 133-134 ° C

[a] <D> 20 = 45.4

TLC: Backing: Merck 0.25mm F 60 or GF 254 silica gel sheet

Fluent: hexane: butyl acetate. methanol - 3: 5: 2

Detector: U.V. plate exposure (250 (?) M) for at least 30 minutes

Rf = 0.56

Elementary analysis

H N

% calc. : 62.00 6.50 10.84

% found : 61.90 6.52 10.82

Example 5

3,5-diicdo-4-p-methoxyphenyl-N-ac9tyl-L-phenylalanine ethyl ester

Preparation of the ioduring solution

50 Kg of water, 8.5 Kg (51.2 moles) of KI, 7.4 Kg (29.2 moles) of raw iodine and 72 Kg of acetone are loaded into a reactor and the mixture obtained is cooled to 20 ° C about and stirred until complete solution.

Preparation of the diazonium salt

In a second reactor, 30 Kg of acetic acid and 6 Kg (15.5 moles) of the diamine obtained as described in ex. 3 and the mixture is cooled to 20-25 ° C and stirred until complete solution. 48 Kg of sulfuric acid monohydrate are then poured into the solution obtained and, after having cooled to a temperature between -10 and -15 ° C, a solution of 2.4 kg (34.8 moles) of sodium nitrite in 9 kg of water. Finally, a solution of urea (0.150 kg; 2.5 moles) in 300 ml of water is added. The solution thus obtained is poured in 30-50 minutes in the first reactor containing the ioduring solution maintained at a temperature of 15-20 "C After the addition, the mixture is treated with a solution of sodium bisulfite (6 kg) in water (18 kg) and diluted slowly with a further 300 kg of water obtaining precipitation of the product which is filtered, washed with water and dried (8 kg , 4; yield 89%).

[a] D20 = 30.7

TLC: Support: ready-made 60 F 254 Merck silica gel plate Eluent: tetrachlorethylene: cyclohexane. B.C. acetic - 6: 2: 2 Detector: U.V. light of 254 nm or development of the spots by "spraying" a 1% aqueous solution of starch solder and subsequent exposure of the plate. U.V. of 254 nm for 5 minutes.

Rf = 0.37

Elementary analysis

c H I N

% calc. : 39.43 3.47 41.66 2.30

% found : 39.50 3.47 41.62 2.29

Example 6

Preparation of 3,5-L-diiodothixonin

2.2 Kg of acetic acid, 3.2 Kg of hydrogen iodide and 2.4 Kg (3.94 moles) of the product obtained in Example 4 are loaded into a reactor and the mixture obtained is heated. At 80-85 ° C the boiling of the lowest boiling fractions begins, which are distilled and eliminated. The temperature is then brought to 105-110 ° C and maintained at this value for 5 hours. At this point the reaction mixture is added with 0.9 kg of hydrochloric acid, kept under stirring at the aforementioned temperature for a further 2 hours and then cooled to 90 ° C, with the addition of a sodium bisulfite solution (110 g in 2 Kg of water) and further diluted with water (15 Kg). The mixture is then cooled to 20 ° C and kept under stirring at this temperature for one hour obtaining precipitation of the product which is filtered and washed with water. The wet product thus obtained is purified by solution with bases (sodium hydrate 30%) at pH 12-12.5, filtration and hot reprecipitation (60 ° C) with acetic acid at pH 5-5.3 obtaining the product in question (Kg 2, 0; yield 96.7%).

HPLC: 99.7% (area%)

Chromatographic conditions

Column: Lichrosper CN, 5 μm, length 25 cm, d. i.4 mm)

mobile phase: water - acetonitrile - acid - phosphoric 85%: 600-400-0.5 flow: 1.0 ml / min

revelation 225 nm

Elementary analysis

C H I N

% calc .: 34.31 2.49 48.33 2.67

% found: 34.3 2.51 48.30 2.65

[a] <D> 2o = + 28.3

The 1H-NMR, 13C-NMR, IR and MS spectra are in agreement with the indicated structure.

Example 7

Preparation of the monoscdic salt of L-thyroxine

9 Kg of deionized water, 1 Kg (1.9 moles) of 3,5-diiodo thyronine and, in a 70% N-ethylamine, are fed into a reactor while maintaining the temperature of the reaction mixture between 20 and 22 ° C. In the sol maintained at the indicated temperature, a solution of iodine (1.05 kg) and potassium iodide (1.75 kg) taxium (1.75 kg) taxium (1.75 kg) is poured into deionized water in about three hours (6 Kg). The mixture obtained is kept under stirring at the indicated temperature for about an hour, then it is decoloured with a solution of sodium bisulfite (25 g) and sodium hydrosulfite (5 g) in 1 liter of water. -50 ° C and the crude product is precipitated by adding acetic acid (0.8 kg) in about 30 minutes at a pH between 5 and 5.5.

During the precipitation the temperature of the mixture rises spontaneously up to 80-85 ° C so that, before proceeding with the centrifugation of the product itself, bring the temperature of the mixture to about 40 ° C. The iodination product is then repeatedly washed in centrifuge with deionized water (50 kg total) at 90 ° C and dried obtaining L-thyroxine as free base (1.43 kg; yield 97%). The compound thus obtained (1.8 moles) is loaded into a reactor previously washed with nitrogen and diluted with 9 kg of absolute ethanol. In the suspension obtained, heated to 55-60 ° C, a solution of sodium hydrate (250 g) in deionized water (250 g) is then poured. The mixture is then slowly cooled to 18-20 ° C under a light flow of nitrogen and then centrifuged. The disodium salt of L-thyroxine thus obtained is washed with absolute ethanol (1.4 kg) and isolated as a wet compound which is used as such in the preparation of the monosodium salt.

The previously obtained wet compound is then loaded into a reactor which is diluted with deionized water (17 liters) and brought to complete solution by adding 30% sodium hydrate up to pH 12.1-12.5 ° (100 g), moderately heating , if necessary, up to 25-30 ° C. At this point, 10 g of Carbopuron and 25 g of sodium sulphite are added and it is left to decolourise for 30 minutes. The solution is then filtered on a cartridge with pores of 0.45 (?) M, the filter is washed with water (1 Kg) and HC1 FU is poured into the solution obtained up to pH 2-3 (500 g) which causes precipitation of L-thyroxine. In the suspension thus obtained, heated to 70 - 80 ° C, a solution of sodium carbonate (2.4 Kg) in water (7 Kg) heated to 90 ° C is added. The mixture is then heated to 90-95 ° C until the complete solution of the partially precipitated product is obtained, then carefully cooled. At a temperature between 88 and 80 ° C, the crystallization of monosodium L-thyroxine occurs. The temperature is further lowered in about three hours up to 40 ° C then the cooling continues, without particular precautions, up to a temperature below 20 ° C. The product is centrifuged and washed in a centrifuge with deionized water (2 kg), dried to obtain 1.3 kg of sodium salt of the levo thyroxine pentahydrate (yield 77%).

HPLC100.3% (area%)

Melting point: 235 ° C (decomposition)

Elementary analysis

C H I N Na

% calc .: 22.55 1.26 63.54 1.75 2.88

% found: 22.57 1.26 63.48 1.75 2.87

The 1H-NMR, 13C-NMR, IR and MS spectra are in agreement with the indicated structure.

[a] <D> 20 = 19.4

Example 8

Preparation of L-thyroxine as a free base

In a reactor 40 g of disodium salt still partially moist (corresponding to 36 g of dry product) are suspended in 550 g of water and the suspension is pulped and finally brought to complete solution by adding small quantities of 30% NaOH, up to pH 12.2-12.5. In the solution obtained, decoloured with Carbopuron 4N (1 g), filtered, and heated to 60 ° C, glacial acetic acid (about 12 g) is then quickly poured, obtaining the precipitation of L-thyroxine as a free base. During precipitation, the pH of the solution must be kept between 5 and 5.5 by possibly adding small quantities of acetic acid. The suspension is then heated to 80-85 ° C and kept under stirring for one hour. During the precipitation there is therefore a spontaneous cooling of the same to 40 ° C. The product is filtered, washed with water heated to 80 ° C, dried, obtaining 32.1 g of L-thyroxine as free base (yield 97%).

HPLC99.4% (area%)

[a) <D> 20 = 19.8

Elementary analysis

C H I N

% calc .: 23.19 1.43 65.33 1.80

% found: 23.14 1.43 65.26 1.79

The 1H-NMR, 13C-NMR, IR and MS spectra are in agreement with the indicated structure.

Example 9

Preparation of 3,5,3 '-L-triiodothyronine and the corresponding monosodium salt

7 Kg of deionized water, 1 Kg (1.9 moles) of 3,5-diiodothyronine and, in one hour, 5.1 Kg of 70% N-ethylamine are loaded into a reactor, maintaining the temperature of the reaction mixture. between 20 and 22 ° C. In the solution obtained, maintained at the indicated temperature, a solution of iodine (0.455 Kg) and potassium iodide (0.69 Kg) in deionized water (3.4 Kg) is poured in about 3 hours The solution is kept stirred at said temperature for about an hour and then is decoloured by treatment with sodium bisulfite (25 g) and sodium hydrosulfite (5 g) in one liter of water. The solution is then heated to 45-50 ° C and the crude product is precipitated by addition in about 30 minutes of acetic acid at a pH between 5 and 5.5 consuming about 0.7 kg of acid. The suspension is slightly cooled to about 40'C and centrifuged. The product obtained is repeatedly washed with deionized water heated to 90 ° C and dried to obtain L-3,3 ', 5-triiodothyronine as free base (1.2 Kg; 1.8 moles). The crude compound thus obtained is loaded into a reactor previously washed with nitrogen and suspended in 5 liters of ethanol and in said suspension, heated to 50-55 ° C, a solution of sodium hydrate (330 g) in deionized water is poured ( 330 g) obtaining first dissolution and then precipitation of the disodium salt. The mixture is then slowly cooled to 18-20 ° C under a light flow of nitrogen and then centrifuged. The isolated disodium salt is washed with ethanol (1.5 kg overall) and the wet product obtained (1.8 moles) is used as such in the preparation of the corresponding monosodium salt and the pure free 3,5,3'-triiodothyronine base.

Preparation of the monosodium salt of 3,5, 31-L-triiodothyronine The previously isolated wet disodium salt (1.8 moles) is loaded into a reactor, diluted with deionized water (12 liters) and solubilized by adding sodium hydrate 30% up to pH between 12.2 and 12.5 (100 g total) and heating moderately, if necessary, up to 25 ° C. The solution thus obtained is then decoloured by adding 5 g of Carbopuron and 25 g of sodium sulphite, filtered on filter with pores of 0.45pm and the filter is washed with water (1 Kg). HCl FU is then poured into the solution up to pH 2-3 (350 g) obtaining precipitation of triiodothyronine. In the suspension thus obtained, heated to 75 ° C, a solution of sodium carbonate (1.7 kg) in water (5 kg) heated to 75 ° C is added and the suspension is kept stirred at the indicated temperature until complete solution is obtained. Said solution is then carefully cooled and at a temperature of about 50 ° C there is crystallization of monosodium 3,31,5-triiodothyronine. The cooling is then continued with caution and slowly up to 40 ° C and then, without particular precautions, until at 20 ° C. The product is then centrifuged and washed in a centrifuge with deionized water (2 kg) and dried to obtain 1 kg of sodium salt of 3,3 ', 5-triiodothyronine (yield 82% with respect to the corresponding disodium salt).

HPLC: 99.1% (area%)

[a] <D> 20 = + 21.4

Elementary analysis

C H I Na N

% calc .: 26.77 1.65 56.57 3.42 2.08

% found: 26.79 1.65 56.60 3.41 2.08

The 1H-NMR, 13C-NMR, IR and MS spectra are in agreement with the indicated structure.

Preparation of 3,5,3'-triiodothyronine as a free base

In the preparation of 3,5,3'-triiodothyronine, the previously obtained wet disodium salt is loaded into a reactor and suspended in deionized water (12 liters). 3,3 ', pure 5-triiodothyronine as a free base. During precipitation, the pH of the solution must be kept between 5 and 5.5 by possibly adding small quantities of acetic acid. The suspension is then heated to 80-85 ° C and kept stirring for one hour and then cooled. The product is filtered, washed with water heated to 80 ° C and dried. Yield: 96%.

HPLC: 99.4% (area%)

[a] <D> 20 = + 22.6

m.p. : 227.6 ° C

Elementary analysis

% cale. : 27.67 1.86 58.48 2.15

3⁄4 found : 27.63 1.86 58.42 2.15

The 1H-NMR, 13C-NMR, IR and MS spectra are in agreement with the indicated structure.

Preparation of D-thyroxine

The D-enantiomer of thyroxine is prepared similarly to that L starting from D-tyrosine or starting from D-dinitrothyrosine obtained by optical inversion of the dinitro derivative of L-tyrosine itself (compound II) where said inversion is carried out as described in the literature (J.Elks and G.J. Waller, J.Chem. Soc., 1952,2366) and as indicated in SCHEME II.

Example 10

Isolation of the disodium salt of D-thyroxine

0, 1 kg (0.19 moles) of 3,5-D-diiodothyronine and 0,62 kg of 70% monoethylamine in 0.90 kg of water are solubilized in a reactor. In the solution, cooled to about 20 ° C, a mixture consisting of 0.5 kg of deionized water, 0.175 kg of potassium iodide and 0.105 kg of iodine is poured in about 2 hours. At the end of the casting, the solution is left under stirring for 30 'and then is decoloured by adding a solution of sodium bisulfite (2.5 g) and sodium hydrosulfite (0.5 g) in water (75 g). The mixture obtained is then heated to 50 "C, and the crude tetraiododerivato is precipitated by the addition of glacial acetic acid (0.65Kg) obtaining simultaneous raising of the temperature to about 75 ° C. The mixture is cooled to 50 ° C and after 3 hours is filtered. The product is repeatedly washed with hot water (90 ° C) and the isolated wet product is suspended in 1 kg of absolute ethanol. The suspension is heated to 50 ° C, pulped and finally added with a solution of NaOH ( 0.025 Kg of tablets in 0.025KG of deionized water) obtaining solution. The solution is then left to cool spontaneously for an hour during which the disodium salt precipitates, then it is further cooled to 16 ° C and the precipitate is filtered, washed with absolute ethanol. By drying under vacuum, at 40 ° C, the disodium salt of 3,5,3'-D-triiodothyronine (0,143 Kg) is obtained which still contains 5.6% of water and 4.4% of ethanol abs auto.

The corresponding monosodium salt and the free base are prepared analogously to the corresponding L-enantiomers.

Claims (21)

CLAIMS 1. Process for the production of thyroid hormones and / or their salts with alkali metals as well as their derivatives which includes the following steps: 1) nitration of L-tyrosine and isolation of the dinitro-derivative as sodium salt; 2) protection of the amino group of dinitro-L-tyrosine with a suitable protective group; 3) protection with an appropriate protective group of the carboxylic function of the product obtained in stage 2; 4) condensation of the product of step 3 with p-methoxyphenol; 5) reduction, with a suitable reducing agent, of the product of said condensation to the corresponding diamino derivative; 6) diazotization with H2SO4 and an aqueous solution of a suitable nitrite of the diamine dissolved in a suitable acid or mixture of acids; 7) iodination of the diazonium salt with a solution of iodurants in a suitable solvent and / or mixture of solvents which favor the precipitation of the diiododerivato obtained; 8) saponification with a suitable acid or mixture of acids of the protective groups of the product of step 7; 9) iodination of the saponification product, precipitation of the obtained crude hormone and subsequent purification of the same by crystallization of the corresponding disodium salt; 10) isolation of the sodium salt of said hormone, or of the same as a free base, starting from the corresponding disodium salt. 2. Process according to claim 1 for the production of L-thyroxine which comprises the following steps: 1) nitration with HNO3 at a temperature between 10 and 30 ° C of the L-tyrosine dissolved in H2S04, dissolution of the 3,5-dinitro-L-tyrosine obtained in water, neutralization of the solution with a suitable and isolation of the product as salt sodium; 2) N-acetylation of 3,5-dinitro-L-tyrosine with acetic anhydride and a suitable base followed by acidification of the solution to a pH between 1.5 and 2 and isolation of the crystalline product obtained; 3) esterification of the compound obtained in step 2 with diethylsulfite previously prepared starting from ethanol and SOC12; 4) condensation of the compound obtained in step 3 first with the adduct formed by p-toluenesulfonyl chloride and pyridine and then with p-methoxyphenol in pyridine, evaporation of the latter, dissolution of the evaporation residue in a suitable quantity of alcohol, dilution of the alcoholic solution with a suitable quantity of water, plugging it with a suitable base and isolating the diphenylether obtained by crystallizing it from the reaction mixture; 5) catalytic hydrogenation of the dinitro-derivative obtained in step 4 dissolved in a suitable water / alcohol mixture heated to a temperature between 55 and 65 ° C and crystallization of the diamine derivative by cooling the mixture; 6) diazotization of the previously obtained diamine dissolved in CH3COOH with H2SO4 and an aqueous solution of suitable metal nitrite, in the presence of urea, and iodination of the diazotation product by casting the mixture obtained in a solution of ioduring agent in a suitable solvent which favors the precipitation of the diiododerivato by further dilution of the reaction mixture with water; 7) saponification of the protective grains of the compound isolated in the previous stage with a suitable acid or mixture of acids and crystallization of the product by diluting the reaction mixture with water; 8) Iodination with an appropriate ioduring agent and in the presence of ethylamine of the diiodothyronine obtained, decolorization of the solution with sodium bisulfite, precipitation with a suitable acid of the crude L-thyroxine and purification of the same by isolation, from a solution of absolute ethanol and NaOH, the corresponding disodium salt; 9) formation of the monosodium salt of L-thyroxine by adding Na2CO3 to the aqueous solution of the corresponding disodium salt, acidified to a pH between 2 and 5 and heated to a temperature between 70 and 100 ° C; 10) formation of L-thyroxine as a pure free base by acidification of an aqueous solution of the disodium salt corresponding to a pH between 5 and 5.5. Process according to any one of claims 1 and 2 in which the residue obtained by evaporation of the pyridine in stage 4 is taken up with a C1-C3 alcohol. 4. Process according to claim 3 wherein said alcohol is ethanol. 5. Process according to any one of claims 1 to 4 in which said residue, taken up with ethanol, is diluted with water in such a way that ethanol represents between 50 and 90 3⁄4 of said hydroalcoholic mixture. 6. Process according to claim 5 wherein ethanol represents 75% of said hydroalcoholic mixture. 7. Process according to any one of claims 1 and 2 in which the hydroalcoholic mixture obtained in stage 4 is buffered with NaHCCO3. 8. Process according to any one of claims 1 and 2 in which the 3,5-dinitro-derivative of tyrosine is dissolved in a mixture consisting of water and a C1-C3 alcohol in which water constitutes 0-50% of said mixture and then hydrogenated. 9. Process according to claim 8 in which the alcohol is ethanol and water constitutes 20-30% of the mixture. 10. Process according to any one of claims 1 and 2 wherein in the iodination reaction of the diazotation product in stage 6 the solvent in which the iodizing agent is dissolved consists of water or a mixture which comprises, in addition to water, a solvent selected from acetic acid or a C3-C6 ketone. 11. Process according to claim 10 wherein said solvent is acetone. 12. Disodium salt of L-thyroxine in crystalline solid form. 13. Use of the disodium salt of L-thyroxine in crystalline solid form in a process for the production of L-thyroxine. 14. Use of the disodium salt of L-3,5,3'-triiodothyronine in crystalline solid form in a process for the production of L-3,5,3'-triiodothyronine. 15. Process for the preparation of the sodium salt of L-thyroxine in which said compound is isolated starting from the corresponding crystalline solid disodium salt. 16. Process for the preparation of L-thyroxine as a free base in which said compound is isolated starting from the corresponding crystalline solid disodium salt. 17. Process for the production of L-3,5,3'-triiodothyronine as a free base in which said compound is isolated starting from the corresponding crystalline solid disodium salt. 18. Process for the production of the sodium salt of L-3,5,31-triiodothyronine in which said compound is isolated starting from the corresponding crystalline solid disodium salt. 19. Use of the disodium salt of D-thyroxine in crystalline solid form in a process for the production of D-thyroxine. 20. Process for the preparation of the sodium salt of D-thyroxine in which said compound is isolated starting from the corresponding crystalline solid disodium salt. 21. Process for the preparation of D-thyroxine as a free base in which said compound is isolated starting from the corresponding crystalline solid disodium salt.